ISSN 0862-5468 (Print), ISSN 1804-5847 (online) 

Ceramics-Silikáty 57, (1) 53 - 57 (2013)


INFLUENCE OF RARE-EARTH DOPING ON THE ELECTRICAL PROPERTIES OF HIGH VOLTAGE GRADIENT ZnO VARISTORS
 
Ke Lei 1, Yuan Yanhong 1, Zhao Hua 1, Ma Xueming 2
 
1 Institute of Applied Mathematics and Physics, Shanghai Dianji University, Shanghai 201306, P. R. China
2 State Key Laboratory of Precision Spectroscopy, Department of Physics, East China Normal University, Shanghai 200241, P. R. China

Keywords: ZnO varistors, Rare-earth doping, Voltage gradient, Electrical properties
 

The influence of rare-earth doping on the electrical properties of ZnO varistors was investigated. In a lower doping region, the electrical properties were greatly improved with the increase of rare-earth contents. The highest voltage gradient value of 1968.0 V/mm was obtained with a rare-earth concentration of 0.06 mol. %. The microstructure of samples with different amounts of rare-earth oxides was examined and the notable decrease of grain size was identified as the origin for the increased voltage gradient. The doped rare-earth oxides dissolved at the grain boundaries and the excessive doping reduced the voltage across the single grain/grain boundary from 2.72 V to 0.91 V. The poor electrical properties in a higher doping region resulted from the degeneration of grain boundaries and the decrease of block density.


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